1824.] M. Gai/-Limac on the Chloride of Lime. 225 



as is necessary to give the greenish colour, and the assay once 

 more renewed by putting into the tube a quantity of the tincture, 

 equal to that discoloured in the preceding assay. The mani- 

 pulations of this experiment are precisely the same as those of 

 the first; but since the results are similar, and it requires the 

 tubes K and L in addition, I do not consider it as preferable to 

 the former. 



It may be convenient to some of our readers if we reduce the 

 French weights and measures employed by M. Gay-Lussac, in 

 the preceding very valuable paper to equivalent English ones. 



100 cubic inches of pure dry chlorine, at the mean pressure 

 and temperature of 30 inches and 60° Faht. weigh 75*375 grains, 

 1 volume of which discolours 10 volumes of the proof tincture. 



■ Suppose we take 250 grains of chloride of lime and dissolve 

 it in 100 cubic inches of water, and that we find the value of 

 this solution to be denoted by 7-6°, or, in other words, that 

 1 cubic inch of the solution discolours 7-6 cubic inches of proof 

 tincture; then the whole quantity, or 100 cubic inches of the 

 solution of chloride, would discolour 760 cubic inches of tinc- 

 ture, one-tenth of which, or 76 cubic inches, is the quantity of 

 chlorine it contains. 



250 grains = ^th of a pound avoirdupois; consequently, 

 lib. of chloride of lime of the above quality would afford 

 (28 x 76) = 2128 cubic inches of chlorine, or rather less than 

 1^- cubic foot, or about 138 cubic feet per cwt. 



Assay of the Oxide of Manganese. 



Pure peroxide of manganese is composed of 



Manganese 28 grains 



Oxygen 16 



44 



and affords 36 grains of chlorine, or 47-76 cubic inches at mean 

 pressure and temperature ; consequently 92" 127 grains will give 

 100 cubic inches, and 1 lb. will give 4*397 cubic feet. 



We take therefore 92*127 of the oxide to be assayed, and treat 

 it as directed, p. 221, receiving the disengaged chlorine in rather 

 less than 100 cubic inches of milk of lime, which, after the 

 operation, must be made exactly equal to that quantity by pure 

 water, and assayed as above. The result will indicate the 

 quality of the oxide of manganese in cubic inches of chlorine, 

 per 92*127 grains of ore. 



To coincide with these weights and measures, the small 

 weight B should be equal to 125 grains : the capacity of the 

 jar G to the arrows, 50 cubic inches, and that of the little mea- 

 sure or tube F, -^of a cubic inch. Each of the large divi- 

 sions on the tubes I and K, must also be equal to * - of a cubic 

 inch, to correspond with the capacity of the small measure F, 

 New Series, vol.. vilff. «v 



